-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KOKX 230904
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
504 AM EDT Mon Apr 23 2018

.SYNOPSIS...
High pressure centered over the Northeast will drift offshore
today, and further over the Atlantic on Tuesday. Low pressure
will affect the region Tuesday Night into Wednesday Night.
Another low pressure or frontal system may affect the region
Friday or Saturday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
It was skc this mrng across the fcst area. A 1032 high was
centered over VT/NH at 3am per msas. This high will drift
off the coast today. Light winds, gaining a sea breeze
component this aftn, and sunny skies can be expected. A blend of
the MET/MAV was used, which takes areas w of the Hudson River
close to 70.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...
The high will continue to slide ewd thru the period, allowing
low pres over the Southeast to draw closer to the cwa. The
models have been consistent in holding off on pcpn until Tue
eve, so pops have been scaled back during the day on Tue. Main
challenge will be clouds, as the modeling suggests a dense
cirrus developing as early as tngt. Water vapor imagery supports
the supply of moisture, so clouds have been ramped up late tngt
and all of Tue. Tue looks mainly ovc attm. This cloud shield
should keep temps from bottoming out like they did this mrng,
so the fcst has been warmed abv guidance. Of course, if clouds
don`t increase as expected tngt, temps will verify lower than
fcst. With a lgt onshore flow, there could be some patchy fog.
The Superblend was used for Tue, with the increasing sely flow
limiting temps.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Models continue in good agreement with a large southern closed upper
low over the Tennessee River Valley Tuesday, opening and lifting
into the NE US through Wednesday in response to northern stream
shortwave energy moving into the upper Midwest/Great Lakes. At the
surface, resultant low pressure lifts towards the region Tuesday
Night into Wednesday, and then to the north Wed Night/Thu. One
interesting feature to be watched, that is being picked up by the
operational models (very clearly in the NAM), is development of a
sub-tropical wave within WCB convection off the SE coast Tuesday.
This features then rides north up the coast in the WCB and either
merges or swings around the primary low as it approaches the region
Wed.

Overall, a soaking rain with breezy E/SE winds is expected to
develop across the area late Tuesday night and continue into
Wednesday afternoon. Timing differences still exist on timing of
heaviest rain, during the late Tuesday Night into Wed afternoon time
period. Can`t rule out an isolated thunderstorm Wed morning into
afternoon along/ahead of approaching warm front with weak elevated
instability and forcing from approaching shortwave energy and 55-65
kt SE llj. Most operational solutions are muted with the development
of a sub-tropical wave, keeping rainfall to a 1/2 to 1 inch event.
Meanwhile the NAM is denoting potential for a heavier rainfall with
a stronger wave and sub-tropical Atlantic moisture inflow, resulting
in a 1 to 2 inch rainfall. This interaction will have to be
monitored over the next 24 to 36 hrs, as the NAM may be resolving a
convectively induced wave better than other operational guidance. In
any case, have increased QPF to 3/4 to 1 1/2 inches based on upward
trend in GEFS and SREF mean and mode, and to capture potential for
the stronger sub-tropical connection noted in the NAM.
Interestingly, the operational GFS is a the bottom of the envelope
of QPF spread of GEFS members. Highest QPF amounts are favored
across NYC metro, NE NJ, Lower Hudson Valley and SW CT with
orographic lift of moist SE inflow. Otherwise, models in general
agreement with best forcing/moisture move NE Wed afternoon into Wed
Eve, with lingering showers Wed NIght, a slower trend than 24 hrs
ago.

Thereafter, models still have notable spread in the evolution of the
above mentioned Upper Midwest/Great Lakes trough, as its energy
splits N/S during the mid to late week period. Differences exist in
the strength of the southern energy that splits off, and with the
amplification of the northern energy over the Eastern Great Lakes
and Northeast Wed Night/Thu as it phases with the initial southern
wave moving up the coast. This is further complicated by differences
in evolution of the next northern stream shortwave diving into the
Central US for late week, that does a similar split. It appears the
evolution of the northern portion of this energy, and the
interaction (if any), with the southern energy that got left behind,
will be a key determinant in sensible weather for Fri/Sat. So a
complex forecast to say the least. At this point, it appears
there is potential for a progressive low pressure or frontal
system to affect the region during the Friday or Saturday time
period, but predictability on details remains low. Will continue
with low chance of showers in the forecast during this time to
denote the potential.

Temperatures during this time period will be seasonable, except a
few degrees below seasonable Wednesday with low pressure
affecting the region. In fact, if the more progressive/less
amplified solutions are correct, Thursday into Saturday could be
slightly above seasonable, pushing 70 for NYC/NJ metro and
solidly in the 60s elsewhere.

&&

.AVIATION /09Z MONDAY THROUGH FRIDAY/...
-- Changed Discussion --
High pressure moves across the terminals through midday and then
moves offshore for the remainder of the TAF period.

VFR conditions are expected through the TAF period with mostly
clear conditions through much of the TAF period. Winds will be
light and variable initially, eventually becoming NE-E near 5 kt
this morning and then S-SE 5-10 kt late this morning into this
afternoon.

Expect some variance of 1-3 hours at individual terminals with
the timing of the wind direction shifts. Winds become lighter
and more southerly tonight.

...NY Metro Enhanced Aviation Weather Support...

Detailed information, including hourly TAF wind component fcsts,
can be found at:
http://www.weather.gov/zny/n90

KJFK TAF Comments: Amendments possible with wind shift timing
from NE to SE, which could vary 1-3 hours from forecast.

The afternoon KJFK haze potential forecast is GREEN, which implies
slant range visibility P6SM outside of cloud.

KLGA TAF Comments: Amendments possible with wind shift timing
from NE to SE, which could vary 1-3 hours from forecast.

The afternoon KLGA haze potential forecast is GREEN, which implies
slant range visibility P6SM outside of cloud.

KEWR TAF Comments: Amendments possible with wind shift timing
from NE to SE, which could vary 1-3 hours from forecast.

The afternoon KEWR haze potential forecast is GREEN, which implies
slant range visibility P6SM outside of cloud.

KTEB TAF Comments: Amendments possible with wind shift timing
to SE, which could vary 1-3 hours from forecast.

KHPN TAF Comments: Amendments possible with wind shift timing
to SE, which could vary 1-3 hours from forecast.

KISP TAF Comments: Amendments possible with wind shift timing
from E to S, which could vary 1-3 hours from forecast.

.OUTLOOK FOR 06Z TUESDAY THROUGH FRIDAY...
.Late tonight...VFR.
.Tuesday...Lowering VFR cigs. SE winds G20KT especially near
the coast.
.Tuesday Night...Rain with MVFR conds developing in the evening,
then IFR conds likely after midnight. SE winds G20KT at times.
.Wednesday...Rain with IFR conds. E-SE winds G20-25KT.
.Thursday-Friday...Mainly VFR.
-- End Changed Discussion --

&&

.MARINE...
Winds and seas will remain blw sca lvls thru Tue.

Low pressure moving up the eastern seaboard Tuesday into Wednesday
will result in strengthening easterly winds and building seas
Tuesday Night, with SCA conditions likely to returning Tuesday Night
and continuing into Wednesday afternoon.

Winds likely subside below SCA late Wed into Wed Eve as low pressure
moves over and then NE of the region, and could remain sub-SCA into
the weekend. Ocean seas will likely be slower to subside, likely
remain elevated at SCA levels into Friday from residual SE swells.

One caveat, there is low potential for another low to affect the
region Friday with more widespread SCA conds.

&&

.HYDROLOGY...
Dry conditions are expected through Tuesday.

A widespread 3/4 to 1 1/2 inches of rain is likely Tuesday
Night into Wednesday, with heaviest amounts favored across NYC
metro, NE NJ, Lower Hudson Valley, and SW CT. Minor urban and
poor drainage flooding is possible if high end of rainfall
ranges are realized.

There is a low potential for up to 2 inches of rain in the
above mentioned areas, which would increase the threat for
urban/poor drainage flooding, and potentially cause some
localized minor small stream flood impacts.

&&

.EQUIPMENT...
NYC NOAA Weather Radio Station KWO-35 (162.55 MHz) remains off
the air.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...None.

&&

$$
SYNOPSIS...JMC/NV
NEAR TERM...JMC
SHORT TERM...JMC
LONG TERM...NV
AVIATION...JM
MARINE...JMC/NV
HYDROLOGY...JMC/NV
EQUIPMENT...